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>G.4. Extensions</A
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>   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> is designed to be easily extensible. For
   this reason, extensions loaded into the database can function
   just like features that are built in. The
   <TT
CLASS="FILENAME"
>contrib/</TT
> directory shipped with the source code
   contains several extensions, which are described in
   <A
HREF="contrib.html"
>Appendix F</A
>.  Other extensions are developed
   independently, like <SPAN
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><A
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></SPAN
>.  Even
   <SPAN
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>PostgreSQL</SPAN
> replication solutions can be developed
   externally. For example, <SPAN
CLASS="APPLICATION"
> <A
HREF="http://www.slony.info"
TARGET="_top"
>Slony-I</A
></SPAN
> is a popular
   master/standby replication solution that is developed independently
   from the core project.
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